BIOL111 Lecture 3
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In which geological era did prokaryotes first appear?
How can we define diversity in life or biodiversity?
- Degree of differences in:
- genetic variation
- species composition
- interactions within and between ecosystems
What is species diversity?
commonly reserved for indices that measure both the number of species in a habitat as well as their relative abundances
How many species have already been named?
about 1.5 million
How many new species are named each year?
- about 13,000
- but about 3,000 are synonyms (duplicated species)
What is tree fogging?
- technique designed by Terry Erwin in 1983
- fog one tree, killed all the species in it, then classify them all
- found 160 beetle species unique to that tree species, about 50,000 tropical tree species, beetles are about 2/5 of all insects which are about 1/2 of all species
What is the current estimate for extant eukaryotic species?
- 3-100 million
- sir robert may's guess is 7 million
what percentage of all species are extinct?
what is the current estimate for how many bacteria and archaea there are?
about 10,000 bacteria species have been identified but could easily be millions or 100s of millions
What are the 2 main factors that control diversity?
How does area affect diversity?
In general doubling area increases number of species by 10-25%
How does climate affect diversity?
- warm, wet areas have more species
- but we don't know why exactly
Mammals represent ___% of diversity of eukaryotic organisms
Beetles represent ___% of diversity of eukaryotic organisms
What is genetic diversity?
measure of genetic distance (evolutionary separation)
What is functional diversity?
Differences in shape, size, and generally ways of making a living (types of food, places lived, etc)
Which group shows the greatest genetic diversity?
Which group shows the greatest functional diversity?
Where is diversity greatest geographically?
near the equator on large landmasses with good climates
Which group of organisms are the Earth's oldest organisms?
Prokaryotes (2 major groups, bacteria and archaea)
Which domains have a membrane enclosed nucleus?
Which domains have membrane enclosed organelles?
Which domains have peptidoglycan in the cell wall?
What are the defining characteristics of Archaea?
- absence of peptidoglycan in cell wall
- distinctive lipids present in their cell membranes (not found in eukaryotes or bacteria)
- many archaea also have lipid monolayer
How does the DNA of archaea and bacteria differ from ours?
- Have single circular chromosome and plasmids
- Located in the nucleoid region
- chromosome not highly coiled
What are plasmids?
Extra-chromosomal DNA; small rings; easily exchanged during sex
Bactera do not have ________ organelles
What is the use of the cell membrane in bacteria?
highly folded, site of ATP synthesis & photosynthesis
How do bacterial ribosomes differ from eukaryotes ones?
Lack of nucleus, allow simultaneous transcription and translation = fast growth and reproduction
What are the 3 morphological differences in bacteria?
- spheres = cocci
- rods = bacilli
- helical = spirili
How can we determine varieties in cell wall structure in bacteria?
What does it mean if a bacterium is gram positive?
Thick layer of peptidoglycan in the cell wall structure
What does it mean if a bacterium is gram negative?
Thin layer of peptidoglycan in the cell wall structure between 2 membrane layers
typically antibiotics are ineffective against gram _____ bacteria
How do bacteria reproduce?
- rapid, short generation times
- asexual reproduction - "binary fission" - literally divide in half
How do bacteria exchange genetic material?
- 3 main methods to obtain new genetic material
- genes on plasmids are easily transferred
- in conjugation, replicated genes are transferred through hollow tubes called sex pili
How do bacteria maintain homeostasis?
- respond to harsh environmental conditions
- move toward or away from chemicals
what is an endospore?
- something a bacterium forms for protection
- protect bacteria from adverse conditions, helps keep it alive in harsh conditions and for a long time
What is a biofilm?
- bacteria form surface-coating communities called biofilms
- form polysaccharide gel trapping debris and other cells
- can be hundreds of cells thick
- composed of single or many species
- an example is plaque
What is chemotaxis?
The ability of bacteria to move towards or away from chemical signals
How do bacteria perform chemotaxis?
- Use flagella (different than eukaryotes - made from different protein, thinner, more numerous)
- Also glide, roll, use gas floats inside cell
How do bacteria transform energy?
- despite their simplicity in cell structure, prokaryotes are extremely diverse in their metabolic abilities
- variety due to diverse habitats and long evolutionary history
What are photoautotrophic bacteria like?
- Transform light energy into chemical energy = photosynthesis
- absorb light energy with chlorophyll
- use light energy to convert CO2 into glucose
- produce O2 as a waste product
What are aerobes?
obligate aerobes must use oxygen for long-term metabolism
what are anaerobes?
- do not require oxygen for metabolism
- make ATP using fermentation, not cellular respiration
What are obligate anaerobes?
oxygen is toxic to them
What are facultative anaerobes?
use oxygen if it's available
What are aerotolerant anaerobes?
can survive in oxygen environment but do not use oxygen
Most prokaryotes and other organisms do what to get energy?
- they are chemoheterotrophs
- consume organic molecules for carbon and energy source
What are some of the roles that heterotrophic prokaryotes can play in the biosphere?
- symbiosis with eukaryotes (like herbivores)
What do nitrogen fixing bacteria do?
Why is this important?
- convert atmospheric N to NH3
- plants are dependent on nitrogen-fixation
- crop rotation often involves planting legumes (N-fixing bacteria often live on roots of legumes)
How is illness to host caused by pathogenic bacteria?
Caused by toxins
What are exotoxins?
- secreted proteins, very toxic
- example: botulism, tetanus
What are endotoxins?
- outer bacterial membrane, rarely fatal
- example: salmonella and E. coli (food poisoning)
How are bacteria classified?
- Traditionally by shape and gram stain
- Now based more on DNA sequencing
What would you like to do?
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